1. Technical Field
This invention relates generally to the trucking industry and to methods and structure for improving vehicle aerodynamics for better fuel efficiency. It relates more particularly to a semi-trailer or other cargo vehicle having a rear end drag-reducing design.
2. Description of Related Art
The term “cargo vehicle” herein refers to a semi-trailer or other wheeled ground vehicle used for hauling cargo on roads and highways. A typical semi-trailer, for example, includes a large rectangularly shaped, box-like enclosure having a forward end, a rearward end, opposite left and right sidewalls, and opposite floor and roof portions. The left and right sidewalls extend from the forward end to left and right rearward corner portions of the enclosure, with the rearward end being somewhat flat and extending transversely across the direction of forward vehicle travel between the left and right rearward corner portions.
So configured, a cargo vehicle provides efficient use of the space that is available within the size limitations set by various vehicle laws and regulations. Its flat-back design of the rearward end, however, creates a low-pressure region behind the rearward end during forward motion. The low-pressure region results in drag and a corresponding higher rate of fuel consumption.
Numerous semi-trailer refinements and after-market add-on components have been proposed and patented that reduce rear end drag of flat-back enclosures in order to thereby alleviate the fuel-consumption concern. Many existing designs, however, have certain drawbacks. Some include components that extend rearwardly of the enclosure rear end portion where they interfere with the rear doors and with loading dock operations. Others involve complicated and expensive components.
Still other designs require truck-driver participation in installing, removing, and/or adjusting the position of various add-on components. And yet other designs add components that extend laterally beyond maximum width limitations set by laws and regulations, while those that fit within such maximum width limitations are often too restricted in size to function satisfactorily. Thus, the trucking industry needs a better drag-reducing design for the rearward end of vehicles.
The parent application (i.e., U.S. patent application Ser. No. 12/080,654 filed Apr. 4, 2008) describes a cargo vehicle enclosure with left and right rearward corner portions having built-in air deflectors. The left and right rearward corner portions define left and right air passageways that gradually redirect air flowing rearwardly alongside the left and right sidewalls toward a region of low pressure behind the rearward end portion of the enclosure, while avoiding complicated and expensive structure, avoiding interference with truck docking platform operations, requiring no assembly by the vehicle driver, and fitting within the size limitations of various laws and regulations.
Various existing laws and regulations set a 102.375-inch maximum semi-trailer width, plus six inches extra for approved safety equipment and so forth; the total maximum width equals 108.375 inches. Thus, existing add-on deflectors can only be a maximum of three inches wide. By building the deflector in as part of the corner post, each rearward corner portion, and the curved passageway it defines, can occupy 4.1875″ of semi-trailer width without affecting the typical 100.0-inch interior width of the enclosure (i.e., the cargo space). The drag-reducing design makes use of the maximum available semi-trailer width without reducing cargo space.
One embodiment of the enclosure includes left and right rear doors that are multi-panel folding doors (e.g., bi-folding doors). They move to wide-open positions of the doors in which the left and right doors extend outside of the left and right deflector components and forwardly alongside the left and right sidewalls. The doors have jamb panels to which main panels are connected by hinges. Although effective in many respects, the multi-panel bi-folding doors described in the parent application involve some cost and complexity. Thus, a need exists for a better rear door structure on the enclosure.